As used hereinafter, the expression "polyfluoroorgano substrate" means a Teflon.TM. resin, which includes Teflon PFA (perfluoroalkoxy) resin, a copolymer of tetrafluoroethylene and perfluoroalkyl vinylether, Teflon FEP, a copolymer of tetrafluoroethylene and hexafluoropropylene, and Teflon PTFE (polytetrafluoroethylene). These materials are manufactured by E. I. Dupont De Nemours and Co. and are often used as barrier resins. The compositions include thermoplastics and are also used in the electronics industry and the pharmaceutical industry because they have outstanding chemical resistance. Experience has shown, however, that while in most instances, a Teflon resin substrate can serve as an excellent barrier material, permeation of toxic materials in the gas phase can occur through the bulk of the substrate when it is in contact with a liquid containing chemicals having a high vapor pressure. The problem becomes particularly acute when the noxious liquid is at a high temperature.
It would be desirable therefore to provide a Teflon resin substrate which would be suitable for handling a vapor-generating, corrosive medium while substantially precluding the passage of such chemical vapors through the bulk material of the Teflon resin substrate to the external environment.